Hemp is more absorbent in my experience, and bamboo is generally a bit softer.

Hemp fleece (like Babykicks prefolds) is gets rough and stiff, it's also very dense and I had some trouble with it retaining odors. Hemp jersey (like Thirsties hemp prefolds) stays quite soft and has never gotten stinky for me.

I've never had much trouble with either staining.

In my experience, hemp is trimmer and more durable. A lot depends on the type (umm, weave?) of fabric though. Bamboo velour wears quickly for us, but our bamboo prefolds seem to be wearing well. Hemp fleece only worked as pocket stuffers after a month or so because it got so rough/stiff, but hemp jersey stays really nice. HTH!